I don't just think it's just the 747 that could be on its way out, but also the 787 from quite a few fleet futures as well.
Boeing not only seem to have lost their way with the programme, but also to have lost how to keep it sustained and going forward during engineering difficulties. If they are not careful this sort of announcement could start to spread.
Virgin could have had A330s at any time during the last 15 years, and to go for them now seems to show a major change in fleet planning - just like at their half-owner Singapore Airlines, who recently introduced the same type. Many of the recen A330 orders also have Sweetheart Deals on A350s in the fuure, which would be the potential end for the 787 at Virgin, and noted across the rest of the community.